Microsoft has made their latest Security intelligence Report (Eighth Edition) available at their download center and the main elements of the report are available in various formats:

Get Microsoft Silverlight

Microsoft’s SIR v8 Offers Insight and Guidance on Cyber Defense posting at the Microsoft Blog by Vinny Gullotto, General Manager, Microsoft Malware Protection Center

SIRv8 is the most comprehensive intelligence document our team has published to date. The report incorporates data from 500 million systems, providing insight into threat trends in 26 countries. We originally created the SIR to help protect people from Internet-based criminals and attackers. The SIR provides information that helps customers and partners better understand the problem of malicious software, so they can take appropriate action.

Here are the notes and observations just for the United States from the Threat Assessments By Country:

  • The threat landscape in the United States was dominated by malware, which accounted for 72.9 percent of all threats detected on infected computers in 2H09, down slightly from 73.3 percent in 1H09.
  • The most common category in the United States was Miscellaneous Trojans, which includes all trojan families that are not classified as downloaders/droppers or backdoors, and accounted for 35.5 percent of all infected computers. This is up from 33.1 percent in 1H09.
  • The second-most common category was Trojan Downloaders & Droppers, which accounted for 15.8 percent of all infected computers. This is down from 18.9 percent in 1H09.
  • Together, Miscellaneous Trojans and Trojan Downloaders & Droppers made up more than 51 percent of all families detected on infected computers in the United States in 2H09.